To increase processor performance, clock frequencies used by microprocessors, often referred to as xe2x80x9cCPUs,xe2x80x9d have increased. Also, as the number of circuits that can be used in a CPU has increased, the number of parallel operations has risen. Examples of efforts to create more parallel operations include increased pipeline depth and an increase in the number of functional units in super-scalar and very-long-instruction-word architectures. As processor performance continues to increase, the result has been a larger number of circuits switching at faster rates. Thus, from a design perspective, important considerations such as power, switching noise, and signal integrity must be taken into account.
Higher frequencies and data throughput cause a processor to consume increased power and run at increased temperatures. Extreme temperatures can slow the speed of transistors that may cause some CPU activities to be incomplete at the end of a cycle. The effect may lead to loss of data in a CPU or incorrect results; therefore, on-chip temperature sensors are employed for monitoring. The availability of temperature information allows the CPU to reduce the number of activities and/or slow the operating frequency. If scaling the number of activities does not alleviate the condition, a standby or power down mode may be entered to protect the CPU. Accurate temperature information is important to prevent over heating or unnecessary reduction in CPU activities.
Higher frequencies for an increased number of circuits also increases switching noise on the power supply. The switching noise may have a local or global effect. Circuits that create large amounts of noise may be relatively isolated; however, they may also affect other circuits, possibly involving very complex interactions between the noise generation and the function of affected circuits. If the components responsible for carrying out specific operations do not receive adequate power in a timely manner, computer system performance is susceptible to degradation. For example, on-chip temperature sensor accuracy varies with power supply noise. Thus, providing power to the components in a computer system in a sufficient and timely manner has become an issue of significant importance.
FIG. 1 shows a section of a typical power supply network (10) of a computer system. The power supply network (10) may be representative of a single integrated circuit, or xe2x80x9cchipxe2x80x9d, or equally an entire computer system comprising multiple integrated circuits. The power supply network (10) has a power supply (12) that provides power through a power supply line (14) and a ground line (16) to an impedance network Z1 (18). The impedance network (18) is a collection of passive elements that result from inherent resistance, capacitance, and/or inductance of physical connections. A power supply line (22, 23) and a ground line (24, 25) facilitate power supply to a circuit A (20) and circuit B (26), respectively. Power supply line (23) and ground line (25) also supply circuit C (30) through another impedance network Z2 (28) and additional impedance networks and circuits, such as impedance network Zn (22) and circuit N (34). The impedance network and connected circuits may be modeled so that the designer, using a simulator, can better understand the behavior of how the circuits interact and interdependencies that exist.
Still referring to FIG. 1, circuit A (20), circuit B (26), circuit C (30), and circuit N (34) may be analog or digital circuits. Also, circuit A (20), circuit B (26), circuit C (30), and circuit N (34) may generate and/or be susceptible to power supply noise. For example, circuit C (30) may generate a large amount of power supply noise that affects the operation of both circuit B (26) and circuit N (34). The designer, in optimizing the performance of circuit B (26) and circuit N 34), requires an understanding of the characteristics of the power supply noise.
According to one aspect of the present invention, a method for estimating accuracy of an on-chip temperature sensor comprises inputting a representative power supply waveform having noise into a simulation of the on-chip temperature sensor and estimating accuracy of the on-chip temperature sensor from the simulation.
According to another aspect of the present invention, a computer system for estimating accuracy of an on-chip temperature sensor comprises a processor; a memory; and software instructions stored in the memory adapted to cause the computer system to input a representative power supply waveform having noise into a simulation of the on-chip temperature sensor and estimate accuracy of the on-chip temperature sensor from the simulation.
According to another aspect of the present invention, a computer-readable medium having recorded thereon instructions executable by a processor, the instructions adapted to input a representative power supply waveform having noise into a simulation of an on-chip temperature sensor and estimate accuracy of the on-chip temperature sensor from the simulation.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.